White-bearded antshrike (Biatas nigropectus)

Kingdom

Animalia

Phylum

Chordata

Class

Aves

Order

Passeriformes

Family

Thamnophilidae

Genus

Biatas (1)

Size

Length: 17 - 18 cm (2)

Classified as Vulnerable (VU) on the IUCN Red List (1).

The white-bearded antshrike is a distinctive yet secretive bird, thought to be one of the rarest endemic avian species within its range (3). The male white-bearded antshrike is a rich reddish-brown, olive to buff below, with a black cap (2) (3) (4), and a crest which is raised when the bird is excited (5). When the crest is down, the head looks distinctly flattened (6). The lower throat and neck are black and, as the name suggests, there is a white collar, more buffy on the back of the neck, which extends onto the cheeks and chin. A white line is also sometimes visible in front of and behind the eye (2) (3) (4). The beak is quite stout (3) and, unusually for an antshrike, is only moderately hooked (6).

The female white-bearded antshrike is even more secretive than the male (7), and differs in having a reddish-brown crown, a conspicuous white line above the eye, and no black on the throat or breast (2) (3) (4). The female is similar in appearance to the white-collared foliage-gleaner, with which this species often associates (3), but the latter lacks the reddish crown and wings, and has a different beak shape (4). The song of the white-bearded antshrike, given by both the male and female, is a series of six to twelve soft, fairly melodic, high-pitched kiu notes (2) (3) (4), but the species rarely sings spontaneously, and is most easily found using tape-playback (6) (7).

This species inhabits bamboo in lowland and montane Atlantic Forest, up to elevations of 1,200 metres (2) (4). An extreme habitat specialist, the white-bearded antshrike appears to be restricted to areas where certain bamboos, mostly of the generaMerostachys or Guadua, are present (2) (4), and in Argentina it is a specialist on Guadua trinii bamboo (5) (6) (7) (8). It is found mainly in openings and along edges where the bamboo thicket is most extensive and relatively tall (3) (4) (7).

The white-bearded antshrike is not frequently seen in the wild, and is difficult to observe, remaining hidden in the bamboo canopy and not often vocalising (3) (4). Aspects of its biology are therefore not well known. Breeding is thought to occur from October to January (2) (4), and the nest is probably a bowl-like platform, built from dead bamboo leaves and supported by bamboo stems (2). The diet is not well known, but includes larvae from inside bamboo stems (9), ants, spiders, and small seeds (2), with individuals or pairs foraging in dense bamboo stands at up to 10 metres above the ground (2), or occasionally at up to 20 metres (10). Frequent sallies may be made from a perch to glean prey from the undersides of leaves or stems, or prey may be taken directly from adjacent vegetation (2). The white-bearded antshrike is often seen in mixed-species flocks (2), particularly in the company of white-collared foliage-gleaners (Anabazenops fuscus) (3).

Although the white-bearded antshrike is thought to be naturally quite rare, its small remaining populations are fragmented and undergoing a rapid decline (3) (4). The main threat is habitat loss, the Atlantic Forest having suffered rapid destruction and fragmentation as a result of agricultural conversion, urbanisation, mining, plantations and road building (3) (4) (11) (12). Less than ten percent of the original forest may remain (11). To compound this problem, the white-bearded antshrike’s reliance on just a few species of bamboo makes it particularly vulnerable, as the bamboos undergo periodic local die-offs (2) (4) (13). It is not known how the species responds to these bamboo cycles, but strong population fluctuations are likely, making the white-bearded antshrike even more vulnerable to extinction (8). In Argentina, the next widespread die-off event of Guadua trinii is expected in 2018 (13), and it is not known how the population of white-bearded antshrike will respond to this sudden widespread loss of habitat (8).

The white-bearded antshrike occurs in a number of protected areas, including Itatiaia, Serra dos Órgãos and Iguaçu National Parks, Serro do Mar and Desengano State Parks in Brazil (2) (4) (14), and Iguazú National Park (15) (16), Yaboty Biosphere Reserve (17), Piñalito Provincial Park (18), San Jorge Private Reserve, and Cruce Caballero and Urugua-í Provincial Parks (7) in Argentina. However, in Argentina, most records are outside protected areas, especially on farms (5) (7). The Atlantic Forest is considered a Biodiversity Hotspot, and several major conservation initiatives are underway in the region (11). Unfortunately, conservation strategies for the Atlantic Forest have rarely considered bamboo habitat, meaning that this small, rare bird could easily be overlooked in current conservation policies (4). Although large reserves with extensive bamboo are important, more attention needs to be paid to conservation of bamboo habitat outside of traditional parks (5).

Proposed conservation measures for the white-bearded antshrike include more extensive population surveys, studies into its dependence on bamboo and its response to bamboo die-off events, assessment of its bamboo habitat, protection of key areas and environmental education (2) (4) (8). Proyecto Selva de Pino Paraná is already working to raise local awareness of the species around San Pedro and Tobuna in Misiones, Argentina (5).

For more information on the white-bearded antshrike and its conservation see:

Atlantic Forest: a highly biodiverse region found along the east coast of South America, comprising several different vegetation types, including high-altitude grassland, and lowland and montane forest.

Endemic: a species or taxonomic group that is only found in one particular country or geographic area.

Genus: a category used in taxonomy, which is below ‘family’ and above ‘species’. A genus (plural: genera) tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.

Larvae: stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.